Distribution

Birthday Audino

These Audino were distributed at the Pokémon Centers in Sapporo, Tokyo, Yokohama, Nagoya, Osaka, and Fukuoka starting on November 4, 2011. However the Audino wasn't distributed until December 4, 2011 at the Pokémon Center in Tohoku.

Singing Pikachu

The OTs of the Pikachu come from, among other things, the various artists who performed in the events wherein Pikachu was made available. Additional information available here and here.
Due to the Pikachu having eight possible OTs, please refer to the tables below.

OT

The distribution of the Pikachu took place at the concerts to celebrate the tenth anniversary of "a-nation for Life," hence the multiple performers. Also, it was also distributed in various events that promoted the ending theme Can You Name All the Pokémon? BW.